LONDON — Chelsea had two players sent off and lost to visiting Burnley, 3-2, in the first match of its Premier League title defense on Saturday, intensifying the concerns surrounding Chelsea after its frustrating off-season in the transfer market.

The captain Gary Cahill was given a straight red card for a cleats-first lunge in the 13th minute before Chelsea conceded three goals in 20 minutes before halftime. Striker Sam Vokes scored two of them by converting crosses that bookended a stunning volley by left back Stephen Ward.

Chelsea’s Álvaro Morata, a second-half substitute, reduced the deficit after halftime in his first league start since a club-record move from Real Madrid for $75 million.

Hopes of a comeback dwindled when midfielder Cesc Fàbregas was sent off in the 81st after receiving his second yellow card. However, David Luiz ensured a tense finish when he scored in the 88th after being set up by Morata.

The loss will not improve the mood of Chelsea Manager Antonio Conte, who has not hidden his frustration at failing to significantly bolster his squad in the off-season. With Eden Hazard, Tiémoué Bakayoko and Pedro injured and Victor Moses suspended, Chelsea entered the match with a depleted roster.

As a result, Jeremie Boga, a 20-year-old French forward, made his debut. It lasted only 18 minutes before he was sacrificed as Conte reorganized after Cahill’s red card.